The Zintl Phase Eu2Si

Abstract

The Zintl phase Eu 2 Si was synthesized from elemental europium and silicon in a sealed tantalum tube in a high-frequency furnace at 1270 K and subsequent annealing at 970 K. Investigation of the sample by X-ray powder and single crystal techniques revealed: Co 2 Si (anti-PbCl 2 ) type, space group Pnma, a ϭ 783.0(1), b ϭ 504.71(9), c ϭ 937.8(1) pm, wR2 ϭ 0.1193, 459 F 2 values and 20 variables. The structure contains two europium and one silicon site. 151 Eu Mössbauer spectroscopic data show a single signal at an

Valence instability of europium in EuCo2Si2

“…Only the paramagnetic Curie temperature is known for Eu 5 Si 3 , which does not correspond to our data as well [28]. Only structural information is available for Eu 2 Si [29] and for ∼Eu 4 Si [10], ∼Eu 3 Si [30] and ∼Eu 7 Si 3 [10] even those data are unavailable. No magnetic information is available for EuCo 1.5 Si 2.5 , EuCo 0.33 Si 1.67 , EuCo 9 Si 2 and EuCo 9.8 Si 3.2 , but it seems doubtful that they were would order at 73(1) and at 21(2) K: EuCo 0.33 Si 1.67 and EuCo 9 Si 2 were demonstrated to have a dominant divalent valence state of europium [31,32], replacement of the transition metal by silicon stabilises divalent europium in EuNi 2−x Si 2+x [33] and in EuCu 2−x Si 2+x [34], so europium is probably (mostly) divalent in EuCo 1.5 Si 2.5 as well, thus one can compare them with similar isoelectronic gadolinium compounds of close stoichiometry (GdCoSi 3 [35] considered together with GdCo 2 Si 2 [11], GdCo 0.4 Si 1.6 [11] and GdCo 9 Si 2 [36]), which exhibit different magnetic behaviour.…”

Complex physical properties of EuMgSi – a complementary study by neutron powder diffraction and151Eu Mössbauer spectroscopy

“…11,23 While the fits to the spectra appear reasonable, closer inspection reveals that they require a marked increase in linewidth above 8 K (Fig. 12) that clearly reflects behaviour that is being missed by assuming a single unique environment for the europium ions in EuMgSi as T N is approached from below.…”

The ternary Eu-Cu-Si system at 400°C

“…In addition to the already known europium silicides EuSi 2 (α-ThSi 2 type, space group I4 1 /amd) and EuSi (Table 2), two new binary compounds with approximate compositions Eu 7 Si 3 and Eu 4 Si (unknown structures) were found in the system Eu-Si [3]. It should be noted that the binary compound Eu 2 Si [5,6] with PbCl 2 structure type (space group Pnma) was not observed in this study. [7] with CeAl 2 Ga 2 -type structure was confirmed and its homogeneity region was determined (Fig.…”

“…The binary systems bordering the ternary system Eu-Cu-Si are well established. Phase diagrams have been constructed for Eu-Cu [1] and Cu-Si [2]; five compounds have been reported in the system Eu-Si [3][4][5][6].…”